Larynx and Thyroid

For ages 10 to 14 years…

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Larynx and Thyroid Project

The objective of this project is to illustrate some of the deeper structures in the neck and to give you some information related to their function.

Assembly Instructions

Required Materials:   scissors / glue / one empty toilet paper roll

1.   Print the drawings provided. For best results, use a coloured printer.

2.    Cut out all five shapes.

3.   Use the rectangular shape and glue it around the empty toilet paper roll. Make sure that the corresponding lines of the first ring match up behind the roll.

4.   Fold all four bluish parathyroid glands behind the pink shape of the thyroid gland.

5.    Stand the toilet paper roll up. Glue the thyroid gland onto the lower part of the tube to cover both X’s.

6.   Fold the complex shape in the middle to create a V-shape structure.

7.    Fold the back flaps on top of each other to adjust the V-shape to its appropriate width.

8.    Fold the vocal cords on top of the larynx.

9.   Put the triangular cartilage on top of the paper roll.

10.   Use the two other triangular shapes to demonstrate vocal cord problems.

STRUCTURES AND THEIR FUNCTIONS

The model you have constructed has two parts: the upper section which include the thyroid cartilage and its structures and the lower section which includes the trachea with the cricoid ring, the thyroid gland and the parathyroid glands.

UPPER SECTION: thyroid cartilage and its structures.

The upper section of your model corresponds to the Adam’s apple. If you gently push on the most prominent part in the center of your neck underneath your jaw, you will feel the Adam’s apple or thyroid cartilage. This rigid structure is a little bigger in men than in women and acts as the wind pipe. When you breathe, air enters your nose, your throat and then move into the thyroid cartilage, into the trachea (windpipe) and finally into your lungs. The Adam’s apple is made of a special material called cartilage which gives it its much needed rigidity.

This part of the wind pipe has a very unique capability which you can observe very easily. Touch your Adam’s apple and you will feel a vibration when you speak or when you sing. This happens because the vocals cords move inside when they produce sound. Once you have your model put together, you will be able to see the vocal cords by looking at it from the top. You will notice they have a V–shape. The front part remains fixed and the back part moves, constantly changing the width of the V-shape.

This section, which includes the thyroid cartilage, the cricoid cartilage (the first ring of cartilage underneath the thyroid) and the vocal cords, is called the larynx. Vocal cord movement in the airway is produced by a group of muscles that can modify the shape and size of the cords. Each person has a larynx with its own characteristics in terms of size. This is why each person’s voice is different.

When someone’s voice is hoarse, it may due to a change in vocal cord movement or in their shape. If you look at the pieces of your model, you will find two other sets of vocal cords. One shows you vocal cords with two, thicker symmetrical parts. These are vocal cord nodules and they can occur in people who have abused their voice by excessive shouting.

In the second example, you will notice an irritated area located mainly on the right vocal cord with an extension on the opposite side. This is laryngeal cancer and it is mainly related to cigarette smoking and alcohol consumption that has occurred over many years.

LOWER SECTION: the cricoid, the trachea, the thyroid gland and the parathyroid glands.

As mentioned previously, the cricoid cartilage is part of the larynx. It is the first and only complete ring in a series of rings made of cartilage. It is a continuous pipe that brings air to the lungs. All the other rings have a C-shape and do not close. In this part of the airway, there are no vocal cords. Behind the trachea, there is another pipe (not shown in your model) that has a very important role. It is the oesophagus and it takes food from the throat and pushes it down into the stomach.

You know about the thyroid cartilage…the rigid structure in the upper section of your model. There is also something called the thyroid gland. It is the pink, H-shaped structure that you glued on the trachea in your model.

Glands produce hormones which are chemical substances. These substances enter the blood and behave like messengers that travel to every part of your body. The thyroid gland produces three well known messengers: T4, T3 and calcitonin. T4 and T3 are very important hormones because they maintain the activity of many of the organs of the body. If you lacked T4 and T3, you feel mentally and physically tired and slow, have poor resistance to cold and your growth can be slowed down. The other hormone, calcitonin, is important because it acts as a calcium-lowering hormone.

In your model, you will see four bluish, round shapes that are closely associated with the thyroid gland. These are the parathyroid glands. Like the thyroid, these glands send hormones or messengers everywhere in the body. Their messenger is called the parathyroid hormone (PTH). This hormone increases the level of calcium and decrease the level of phosphate in the blood. When you drink a glass of milk, calcium is absorbed from the milk by the digestive tract. The amount of calcium absorbed in the blood has to be regulated very closely. This is where the thyroid and parathyroid glands cooperate to adjust the levels accordingly.

Otolaryngologists are very much involved in the care of patients with problems in this area.

Have fun with this project!